ASTM A194 Grade 7 heavy hex nuts are manufactured from alloy steel, quenched and tempered. The ASTM A194 specification covers carbon steel, alloy steel, and stainless steel nuts for bolts in high pressure or high temperature service. They are a common high strength nut used with stud bolts for high and low temperature service, such as B16 and L7. When low temperature requirements are specified for Grade 7 nuts, the Charpy test procedures and requirements as defined in Specification A320/A320M for Grade L7 will apply. An "L" is added to the grade marking of these nuts. Dimensional specifications are governed by ASME B18.2.2. Heavy hex nuts provide increased bearing surface area over finished nuts such as J995 Grade 5 nuts.